Nearly all vehicle steering mechanisms are equipped with a rotary connector for coupling electrical power and signals between the fixed steering column and the rotatable steering wheel since the steering wheel supports air bag electronics, and in many cases, electrical switches for controlling audio, cruise control and HVAC functions. Two types of rotary connectors are commonly used in vehicles: a sliding contact or slip-ring connector, and a flexible cable or clock-spring connector. These types of connectors have various drawbacks such as generation of audible and electrical noise, a limited number of signal channels, and lack of durability due to wear and contamination.
To overcome the problems associated with the aforementioned rotary connectors, it has been proposed to use a rotary connector in which a metallic conductor (typically mercury) that is liquid at ambient temperatures electrically bridges stationary terminals in the steering column and rotary terminals in the steering wheel; see, for example, the U.S. Pat. No. 5,498,164 to Ward et al., issued Mar. 12, 1996. While the liquid metal approach is potentially advantageous in that it eliminates most noise issues, as well as durability issues due to wear, mercury is no longer approved for usage in consumer applications, and the number of signal channels that can be obtained with a liquid metal connector is quite limited as a practical matter.
The problem with mercury has been solved for many applications such as glass-tube thermometers by the development of a substitute alloy of Gallium, Indium and Tin (available under the tradename Galinstan), which at ambient pressure, remains a liquid between −28° C. and +1300° C. However, this alloy is not suitable for automotive usage because the ambient temperature in an automotive environment may be well lower than the alloy's melting point of −28° C. Accordingly, what is needed is an improved liquid metal rotary connector that is suitable for the automotive environment and that provides an adequate number of power and signal channels.